Great idea- I haven't poured any concrete over foam, though I knew someone that sprayed Rhino Lining over foam for sculptures and it worked really well. I'd try some small tests, but I wonder how the weight of the concrete would work on top of the lightweight foam....

Dave, I know they do concrete or thinset or something over foam for mosaic sculpture but I've just never tried it. My son in law used to own a Line-X dealership and I had access to FREE Line-X but he sold the business. It works awesome over foam but it ain't cheap.
_________________May we all get to have a chance to ride the fast one
Walk away wiser when we crashed one
Keep hoping that the best one is the last one

Rhino lining ain't cheap either.... concrete would be inexpensive to try out... and I'm sure we're all curious if it would work. Actually, I remember someone using concrete over foam in the carving forum a while back? (Maybe in Australia?) I might be remembering something wholly different, though....

Dave's right. When I was researching making concrete tikis for my backyard I saw someone who had put concrete over carved Styrofoam or something very similar.

I just saw the boar on FB so I know you were successful. I need to repair a giant tiki flowerpot I bought at Christmas Tree Shops that has since cracked. I was going to ask you for repair suggestions Mike.
_________________:-)
Lori

I've been taking lots of step-by-step pictures and will post them when my piggie is done, hopefully this weekend. Started with the foam sculpture, added a couple of coats of mortar mix, next a coat or two of concrete vinyl patch with some pigment. Hopefully it will work _________________May we all get to have a chance to ride the fast one
Walk away wiser when we crashed one
Keep hoping that the best one is the last one

The Polynesian Feral Pig (Sus scrofa) seen here in it's adopted tropical habitat. He looks a bit uneasy, maybe he has heard rumor that he is to be the "guest of honor" at the next luau

I decided I wanted a near-life-sized boar in my tropical garden. A ceramic sculpture would have been a fun challenge for me with lots of texturing and glazing opportunities. But I don't have access to a kiln 3 feet long so I decided on concrete over foam with ceramic tusks and eyes. Years ago I picked up a truckload of free Styrofoam blocks and made a vertical heated wire cutter and a horizontal heated wire cutter to work with it. I started with four blocks of foam, each 6x6x34 inches.

I'm not so good at freehanding such things, so I found 3D CAD images of a boar a gridded it out onto the foam blocks.

I cut it out with the heated wire.

Cut all four pieces and glued them together.

Then took a SurForm rasp and finished sculpting the shape. The ceramic tusks and eyes each have a large peg formed onto them to embed them into the Styrofoam.

Here's where I veered off into uncharted waters having never done concrete sculpture before. I mixed up some mortar mix to the consistency of a thick milkshake and started spreading it on the foam (in the kitchen of course ) It covered the horizontal surfaces easily (back & top of head) but was difficult to make it stick to the sides. I ended up just smearing it on the sides, enough to get a thin coating. After this mortar was set, I applied another layer. The next layer was easier to apply, the dry rough concrete of the previous coat allowed the second coat to stick better. I used the second layer to build up some details on the face. Total thickness of the mortar mix was about 1/4 to 1/2 inch.

After the mortar mix cured for a day, I put on a final coat to smooth and color the boar. I used Quikcrete Vinyl Patching Compound which contains very fine sand and adhesion additives. I added 1/4 cup of Quikrete Charcoal Liquid Cement Color to 8 cups of the dry mix and enough water to make a thin slurry, about the consistency of cream of wheat. I spread it on with my hands then used a large paint brush to smooth it out. After the patching mix had set for a little while, I used a stiff brush to make some hair texture on the top of the head and down the middle of the back.

At some point I will put a concrete sealer on it. Since the pigment is embedded in the concrete and the ceramic is glazed he should look good in my garden for years to come

Edit - updated top picture
_________________
When you hurry through life, you just get to the end faster.
Pirate Ship Tree House